Cerebral aggregate g-ratio mapping using magnetic resonance relaxometry and diffusion tensor imaging to investigate sex and age-related differences in white matter microstructure.
Cerebral aggregate g-ratio mapping using magnetic resonance relaxometry and diffusion tensor imaging to investigate sex and age-related differences in white matter microstructure.
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DOI：
10.1016/j.mri.2021.10.019
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发表时间：
2022-01
影响因子：
2.5
通讯作者：
Bouhrara M
中科院分区：
文献类型：
--
作者：
Cortina LE;Kim RW;Kiely M;Triebswetter C;Gong Z;Alsameen MH;Bouhrara M
轴突脱髓鞘是衰老和年龄相关疾病的主要特征。在数学上定义为有髓鞘轴突的内径与外径的g比被用作最佳轴突髓鞘形成的结构指数，并且已被证明代表微结构完整性的灵敏成像生物标志物。几种磁共振成像（MRI）方法的全脑映射的聚合g-比率已被介绍。计算aggerate g-比率需要估计髓鞘体积分数（MVF）和轴突体积分数（AVF）。虽然MVF和AVF的准确测定可以分别通过多组分弛豫法或扩散分析获得，但这些方法需要较长的采集时间，使得它们在临床环境中的实施具有挑战性。因此，需要任何克服这一缺点的尝试。扩展我们以前的工作，我们介绍了一种新的MRI方法的全脑映射的总g比。这种新方法是基于使用单壳扩散进行AVF测定，从我们最近引入的方法中减少了约10分钟的采集时间，同时提供了利用MVF标测的现有数据和AVF标测的单壳扩散数据研究先前研究中g比差异的可能性。我们的比较分析表明，我们新推导出的聚合g比值与我们以前的方法推导出的值相似，这需要更长的采集时间。此外，与我们以前的观察结果一致，我们发现在这个更大的研究队列中，总g比与年龄之间存在二次U型关系。然而，我们的研究结果表明，两性异形的g-比率是不显着的，在任何大脑区域的调查。
Axonal demyelination is a cardinal feature of aging and age-related diseases. The g-ratio, mathematically defined as the inner-to-outer diameter of a myelinated axon, is used as a structural index of optimal axonal myelination and has been shown to represent a sensitive imaging biomarker of microstructural integrity. Several magnetic resonance imaging (MRI) methods for whole-brain mapping of aggregate g-ratio have been introduced. Computation of the aggerate g-ratio requires estimates of the myelin volume fraction (MVF) and the axonal volume fraction (AVF). While accurate determinations of MVF and AVF can be obtained through multicomponent relaxometry or diffusion analyses, respectively, these methods require lengthy acquisition times making their implementation challenging in a clinical context. Therefore, any attempt to overcome this drawback is needed. Expanding on our previous work, we introduced a new MRI method for whole-brain mapping of aggregate g-ratio. This new approach is based on the use of a single-shell diffusion for AVF determination, reducing the acquisition time by approximately ~10 min from our recently introduced approach, while offering the possibility to investigate g-ratio differences in previous studies with existing data for MVF mapping and single-shell diffusion data for AVF mapping. Our comparison analysis indicates that our newly derived aggregate g-ratio values were similar to those derived from our previous method, which requires a longer acquisition time. Further, in agreement with our previous observations, we found quadratic U-shaped relationships between aggregate g-ratio and age in this much larger study cohort. However, our results show that sexual dimorphism in g-ratio was not significant in any brain region investigated.
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